/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   https://www.lammps.org/, Sandia National Laboratories
   LAMMPS development team: developers@lammps.org

   Copyright (2003) Sandia Corporation.  Under the terms of Contract
   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
   certain rights in this software.  This software is distributed under
   the GNU General Public License.

   See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */

/* ----------------------------------------------------------------------
   Contributing author: Trung Dac Nguyen (ORNL)
------------------------------------------------------------------------- */

#include "pair_colloid_gpu.h"

#include "atom.h"
#include "domain.h"
#include "error.h"
#include "force.h"
#include "gpu_extra.h"
#include "memory.h"
#include "neigh_list.h"
#include "neighbor.h"
#include "suffix.h"

#include <cmath>

using namespace LAMMPS_NS;

// External functions from cuda library for atom decomposition

int colloid_gpu_init(const int ntypes, double **cutsq, double **host_lj1, double **host_lj2,
                     double **host_lj3, double **host_lj4, double **offset, double *special_lj,
                     double **host_a12, double **host_a1, double **host_a2, double **host_d1,
                     double **host_d2, double **host_sigma3, double **host_sigma6, int **host_form,
                     const int nlocal, const int nall, const int max_nbors, const int maxspecial,
                     const double cell_size, int &gpu_mode, FILE *screen);
void colloid_gpu_clear();
int **colloid_gpu_compute_n(const int ago, const int inum, const int nall, double **host_x,
                            int *host_type, double *sublo, double *subhi, tagint *tag,
                            int **nspecial, tagint **special, const bool eflag, const bool vflag,
                            const bool eatom, const bool vatom, int &host_start, int **ilist,
                            int **jnum, const double cpu_time, bool &success, double *prd, int* periodicity);
void colloid_gpu_compute(const int ago, const int inum, const int nall, double **host_x,
                         int *host_type, int *ilist, int *numj, int **firstneigh, const bool eflag,
                         const bool vflag, const bool eatom, const bool vatom, int &host_start,
                         const double cpu_time, bool &success);
double colloid_gpu_bytes();

/* ---------------------------------------------------------------------- */

PairColloidGPU::PairColloidGPU(LAMMPS *lmp) : PairColloid(lmp), gpu_mode(GPU_FORCE)
{
  respa_enable = 0;
  reinitflag = 0;
  cpu_time = 0.0;
  suffix_flag |= Suffix::GPU;
  GPU_EXTRA::gpu_ready(lmp->modify, lmp->error);
}

/* ----------------------------------------------------------------------
   free all arrays
------------------------------------------------------------------------- */

PairColloidGPU::~PairColloidGPU()
{
  colloid_gpu_clear();
}

/* ---------------------------------------------------------------------- */

void PairColloidGPU::compute(int eflag, int vflag)
{
  ev_init(eflag, vflag);

  int nall = atom->nlocal + atom->nghost;
  int inum, host_start;

  bool success = true;
  int *ilist, *numneigh, **firstneigh;
  if (gpu_mode != GPU_FORCE) {
    double sublo[3], subhi[3];
    if (domain->triclinic == 0) {
      sublo[0] = domain->sublo[0];
      sublo[1] = domain->sublo[1];
      sublo[2] = domain->sublo[2];
      subhi[0] = domain->subhi[0];
      subhi[1] = domain->subhi[1];
      subhi[2] = domain->subhi[2];
    } else {
      domain->bbox(domain->sublo_lamda, domain->subhi_lamda, sublo, subhi);
    }
    inum = atom->nlocal;
    firstneigh =
        colloid_gpu_compute_n(neighbor->ago, inum, nall, atom->x, atom->type, sublo, subhi,
                              atom->tag, atom->nspecial, atom->special, eflag, vflag, eflag_atom,
                              vflag_atom, host_start, &ilist, &numneigh, cpu_time, success,
                              domain->prd, domain->periodicity);
  } else {
    inum = list->inum;
    ilist = list->ilist;
    numneigh = list->numneigh;
    firstneigh = list->firstneigh;
    colloid_gpu_compute(neighbor->ago, inum, nall, atom->x, atom->type, ilist, numneigh, firstneigh,
                        eflag, vflag, eflag_atom, vflag_atom, host_start, cpu_time, success);
  }
  if (!success) error->one(FLERR, "Insufficient memory on accelerator");

  if (atom->molecular != Atom::ATOMIC && neighbor->ago == 0)
    neighbor->build_topology();
  if (host_start < inum) {
    cpu_time = platform::walltime();
    cpu_compute(host_start, inum, eflag, vflag, ilist, numneigh, firstneigh);
    cpu_time = platform::walltime() - cpu_time;
  }
}

/* ----------------------------------------------------------------------
   init specific to this pair style
------------------------------------------------------------------------- */

void PairColloidGPU::init_style()
{

  // Repeat cutsq calculation because done after call to init_style
  double maxcut = -1.0;
  double cut;
  for (int i = 1; i <= atom->ntypes; i++) {
    for (int j = i; j <= atom->ntypes; j++) {
      if (setflag[i][j] != 0 || (setflag[i][i] != 0 && setflag[j][j] != 0)) {
        cut = init_one(i, j);
        cut *= cut;
        if (cut > maxcut) maxcut = cut;
        cutsq[i][j] = cutsq[j][i] = cut;
      } else
        cutsq[i][j] = cutsq[j][i] = 0.0;
    }
  }
  double cell_size = sqrt(maxcut) + neighbor->skin;

  int **_form = nullptr;
  int n = atom->ntypes;
  memory->create(_form, n + 1, n + 1, "colloid/gpu:_form");
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      if (form[i][j] == SMALL_SMALL)
        _form[i][j] = 0;
      else if (form[i][j] == SMALL_LARGE)
        _form[i][j] = 1;
      else if (form[i][j] == LARGE_LARGE)
        _form[i][j] = 2;
    }
  }
  int maxspecial = 0;
  if (atom->molecular != Atom::ATOMIC) maxspecial = atom->maxspecial;
  int mnf = 5e-2 * neighbor->oneatom;
  int success =
      colloid_gpu_init(atom->ntypes + 1, cutsq, lj1, lj2, lj3, lj4, offset, force->special_lj, a12,
                       a1, a2, d1, d2, sigma3, sigma6, _form, atom->nlocal,
                       atom->nlocal + atom->nghost, mnf, maxspecial, cell_size, gpu_mode, screen);
  memory->destroy(_form);
  GPU_EXTRA::check_flag(success, error, world);

  if (gpu_mode == GPU_FORCE) neighbor->add_request(this, NeighConst::REQ_FULL);
}

/* ---------------------------------------------------------------------- */

double PairColloidGPU::memory_usage()
{
  double bytes = Pair::memory_usage();
  return bytes + colloid_gpu_bytes();
}

/* ---------------------------------------------------------------------- */

void PairColloidGPU::cpu_compute(int start, int inum, int eflag, int /* vflag */, int *ilist,
                                 int *numneigh, int **firstneigh)
{
  int i, j, ii, jj, jnum, itype, jtype;
  double xtmp, ytmp, ztmp, delx, dely, delz, evdwl, fpair;
  double r, rsq, r2inv, r6inv, forcelj, factor_lj;
  double c1, c2, fR, dUR, dUA;
  double K[9], h[4], g[4];
  int *jlist;

  double **x = atom->x;
  double **f = atom->f;
  int *type = atom->type;
  double *special_lj = force->special_lj;

  // loop over neighbors of my atoms

  for (ii = start; ii < inum; ii++) {
    i = ilist[ii];
    xtmp = x[i][0];
    ytmp = x[i][1];
    ztmp = x[i][2];
    itype = type[i];
    jlist = firstneigh[i];
    jnum = numneigh[i];

    for (jj = 0; jj < jnum; jj++) {
      j = jlist[jj];
      factor_lj = special_lj[sbmask(j)];
      j &= NEIGHMASK;

      delx = xtmp - x[j][0];
      dely = ytmp - x[j][1];
      delz = ztmp - x[j][2];
      rsq = delx * delx + dely * dely + delz * delz;
      jtype = type[j];

      if (rsq >= cutsq[itype][jtype]) continue;

      switch (form[itype][jtype]) {
        case SMALL_SMALL:
          r2inv = 1.0 / rsq;
          r6inv = r2inv * r2inv * r2inv;
          forcelj = r6inv * (lj1[itype][jtype] * r6inv - lj2[itype][jtype]);
          fpair = factor_lj * forcelj * r2inv;
          if (eflag)
            evdwl = r6inv * (r6inv * lj3[itype][jtype] - lj4[itype][jtype]) - offset[itype][jtype];
          break;

        case SMALL_LARGE:
          c2 = a2[itype][jtype];
          K[1] = c2 * c2;
          K[2] = rsq;
          K[0] = K[1] - rsq;
          K[4] = rsq * rsq;
          K[3] = K[1] - K[2];
          K[3] *= K[3] * K[3];
          K[6] = K[3] * K[3];
          fR = sigma3[itype][jtype] * a12[itype][jtype] * c2 * K[1] / K[3];
          fpair = 4.0 / 15.0 * fR * factor_lj *
              (2.0 * (K[1] + K[2]) * (K[1] * (5.0 * K[1] + 22.0 * K[2]) + 5.0 * K[4]) *
                   sigma6[itype][jtype] / K[6] -
               5.0) /
              K[0];
          if (eflag)
            evdwl = 2.0 / 9.0 * fR *
                    (1.0 -
                     (K[1] * (K[1] * (K[1] / 3.0 + 3.0 * K[2]) + 4.2 * K[4]) + K[2] * K[4]) *
                         sigma6[itype][jtype] / K[6]) -
                offset[itype][jtype];
          if (rsq <= K[1]) error->one(FLERR, "Overlapping small/large in pair colloid");
          break;

        case LARGE_LARGE:
          r = sqrt(rsq);
          c1 = a1[itype][jtype];
          c2 = a2[itype][jtype];
          K[0] = c1 * c2;
          K[1] = c1 + c2;
          K[2] = c1 - c2;
          K[3] = K[1] + r;
          K[4] = K[1] - r;
          K[5] = K[2] + r;
          K[6] = K[2] - r;
          K[7] = 1.0 / (K[3] * K[4]);
          K[8] = 1.0 / (K[5] * K[6]);
          g[0] = pow(K[3], -7.0);
          g[1] = pow(K[4], -7.0);
          g[2] = pow(K[5], -7.0);
          g[3] = pow(K[6], -7.0);
          h[0] = ((K[3] + 5.0 * K[1]) * K[3] + 30.0 * K[0]) * g[0];
          h[1] = ((K[4] + 5.0 * K[1]) * K[4] + 30.0 * K[0]) * g[1];
          h[2] = ((K[5] + 5.0 * K[2]) * K[5] - 30.0 * K[0]) * g[2];
          h[3] = ((K[6] + 5.0 * K[2]) * K[6] - 30.0 * K[0]) * g[3];
          g[0] *= 42.0 * K[0] / K[3] + 6.0 * K[1] + K[3];
          g[1] *= 42.0 * K[0] / K[4] + 6.0 * K[1] + K[4];
          g[2] *= -42.0 * K[0] / K[5] + 6.0 * K[2] + K[5];
          g[3] *= -42.0 * K[0] / K[6] + 6.0 * K[2] + K[6];

          fR = a12[itype][jtype] * sigma6[itype][jtype] / r / 37800.0;
          evdwl = fR * (h[0] - h[1] - h[2] + h[3]);
          dUR = evdwl / r + 5.0 * fR * (g[0] + g[1] - g[2] - g[3]);
          dUA = -a12[itype][jtype] / 3.0 * r *
              ((2.0 * K[0] * K[7] + 1.0) * K[7] + (2.0 * K[0] * K[8] - 1.0) * K[8]);
          fpair = factor_lj * (dUR + dUA) / r;
          if (eflag)
            evdwl += a12[itype][jtype] / 6.0 * (2.0 * K[0] * (K[7] + K[8]) - log(K[8] / K[7])) -
                offset[itype][jtype];
          if (r <= K[1]) error->one(FLERR, "Overlapping large/large in pair colloid");
          break;
      }

      if (eflag) evdwl *= factor_lj;

      f[i][0] += delx * fpair;
      f[i][1] += dely * fpair;
      f[i][2] += delz * fpair;

      if (evflag) ev_tally_full(i, evdwl, 0.0, fpair, delx, dely, delz);
    }
  }
}
